1. Field of the Invention
The present invention relates to a vacuum regulating valve for the use of, for example, creating a pressure reduction in a chemical-reaction vacuum chamber included in a physical or chemical machine or the like.
2. Description of the Related Art
In a semiconductor manufacturing system, for example, chemical processing such as etching is performed inside a vacuum chamber. In this case, a vacuum pump is used to create a pressure reduction in the vacuum pump, and a vacuum valve is used to open and close an external flowchannel connecting between the vacuum pump and the vacuum chamber. As disclosed in, for example, Patent Document 1, a vacuum valve of the aforementioned type includes two ports individually connected to a vacuum pump and a vacuum chamber, an internal flowchannel interconnecting the ports, a valve seat formed in the internal flowchannel, a valving member that opens and closes the valve seat, and a piston that drives the valving member to perform the open and close operation. The stroke of the piston as it is corresponds to the valve opening in a state where the valving member is open.
However, the vacuum in the vacuum chamber produces fluctuations depending on an increase and decrease in the amount of reaction gases, so that an amount corresponding to the fluctuations has to be compensated for to maintain the interior of the chamber at a necessary vacuum. However, such a vacuum valve is not inherently intended for regulating the vacuum pressure (negative pressure) in a vacuum chamber through the opening of such a valving member. Even if attempt was made to regulate the opening of the valving member, the opening would not be able to be quickly and accurately regulated.
In order to easily regulate the opening of a valving member of a vacuum valve of the above-described type, it is considered appropriate to form a configuration such that a stopper made accurately positionally adjustable is provided, and a piston as described above is driven to the position of abutment with the stopper (see Patent Document 2).
In this case, the positional adjustment of the stopper has to be performed quickly and accurately, so that it is advantageous to drive the stopper by using an electric motor. For the electric motor, a small and inexpensive electric motor can be used if it is used only for positional adjustment of the stopper. However, the piston is compressed thereby at high driving force against the stopper. As such, the stopper has to be supported to withstand the high driving force. In addition, it is difficult to drive the stopper under the effects of the driving force by using a small electric motor, so that countermeasures therefor have to be taken into consideration.
References
(Patent Document 1) Japanese Unexamined Patent Application Publication No. 08-178126
(Patent Document 2) Japanese Patent Application No. 2003-310607